New evidence for 250 Ma age of halotolerant bacterium from a Permian salt crystal

The purported oldest living organism, the spore-forming bacterium Virgibacillus sp. Permian strain 2-9-3, was recently cultured from a brine inclusion in halite of the 250 Ma Permian Salado Formation. However, the antiquity of Virgibacillus sp. 2-9-3 has been challenged; it has been argued that the halite crystal and the fluid inclusion from which the bacterial spores were extracted may be younger than the Permian Salado salts. Here we report that brine inclusions from the same layer of salt that housed Virgibacillus sp. 2-9-3 are composed of evaporated Late Permian seawater that was trapped in halite cement crystals precipitated syndepositionally from shallow groundwater brines at temperatures of 17-37 degrees C. These results support the 250 Ma age of the fluid inclusions, and by inference, the long-term survivability of microorganisms such as Virgibacillus sp. 2-9-3.